The present invention relates to data processors including microcomputers, digital signal processors, microcontrollers and microprocessors especially with debug support features such as emulation. More particularly, the invention relates to a data processor for debugging a microcomputer-based system in a real-use operation environment such as outdoors.
The microcomputer-based system (also called the target system) may be debugged by means of a microcomputer for evaluation use with debug support features. In interfacing the evaluation-use microcomputer to a debugging host system, a large number of signal lines may be used to transmit in parallel data, addresses and control signals equivalent to those of the interface between the microcomputer in question and the target system. However, where the target- system is appreciably small in volume as in the case of a portable communication terminal, it is often impossible practically to equip the circuit board of the system with pins or connectors for connecting numerous signal lines.
One proposed solution to such a bottleneck is the use of a serial interface with the debugging host system. Technical aspects of the solution are discussed illustratively in "DSP 96002 User's Manual" (SECTION 10, ON-CHIP EMULATOR; p10-1.about.p10-22).
The technique described in the publication above involves incorporating in a digital signal processor a command decoder and a break point control circuit for debugging purposes as well as a serial interface for debug use which allows data to be input and output serially in synchronism with a clock signal. Debug commands are fed externally to the processor through the serial interface. The command decoder decodes the commands thus supplied. The decoded result is referenced in controlling write and read operations to and from internal registers as well as in controlling break points.